An ear infection does not usually cause permanent damage to the ear and auditory system, although it can cause tinnitus. When the infection clears up the tinnitus will usually fade away with time.
Middle ear infection can cause permanent damage. Viruses or bacterial toxic metabolites can travel to inner ear and damage structures there. Also hematogenic route is possible (virus travels through the blood).
Interestingly, I saw a paper with autopsy results of inner ears of people who had middle ear infection sometime in their life. Most of them had outer hair cell damage to some degree.
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